ective, early computer drafting systems ran on proprietary workstations which did not operate any other types of software (Rodgers, 1989, p. 5). In these situations, the computer drafting programs used their symbol libraries and blocks to automate the manual drafting process. It was only as computers became faster and more powerful that the unique properties of CAD began to be explored and the CAD process evolved into a tool which moved well beyond merely automating the manual CAD technique.
Although CAD originally simply replaced manual drafting, it is used today in ways such that manual drafting cannot compete. For example, Transom Technologies introduced Transom Jack in the late 1990s as a way to simulate realistic human functions in CAD applications. Transom Jack runs on Silicon Graphics workstations and has been used by NASA to simulate proposed work on the international space station, and to confirm that work done while on the space shuttle will be in an environment which allows astronauts to perform the task successfully. Transom Jack, for example, illustrated that the space station would require footholds in order for astronauts to work successfully ("NASA," 1997, p. 139).
Three-dimensional modeling is one of the application areas which has come out of computer drafting. By displaying images from various perspectives, engineers are able to view prototypes on a computer screen and determine (for example), which compromises lead to the optimal solution for a particular set of parameters. When the product in development has a cost of tens (or hundreds) of millions of dollars, such as military vehicles, the importance of catching design flaws early is critical. Some companies estimate that they have reduced their manufacturing time by half through the use of computer drafting (Teague, 1999, p. 71).
Training is a significant concern with companies implementing computer drafting, and all of the major computer drafting...